Cardiovascular Drugs and Medications Q 67
Amrinone (Inocor) is used for short term therapy for CHF and acts by which of the following mechanisms?
A. Increasing stroke volume and heart rate.
B. Slowing ventricular rate and increasing cardiac output.
C. Vasodilating and increasing peripheral vascular resistance.
D. Increasing cardiac output and enhancing renal perfusion.
Correct Answer: A. Increasing stroke volume and heart rate.
The action of amrinone (Inocor) is to increase stroke volume, ejection fraction, and heart rate. Inamrinone, also known as amrinone, is a drug that increases cardiac output through its positive inotropic and vasodilatory effects. It is prescribed for the short-term management of congestive heart failure, relieving symptoms of the condition such as fatigue, weakness, edema, dyspnea orthopnea, and paroxysmal nocturnal dyspnea.
Option B: Lanoxin, not amrinone, slows ventricular rate, and increases cardiac output. It increases the force of contraction of the heart by reversibly inhibiting the activity of the myocardial Na-K ATPase pump, an enzyme that controls the movement of ions into the heart. Digoxin induces an increase in intracellular sodium that will drive an influx of calcium in the heart and cause an increase in contractility. Cardiac output increases with a subsequent decrease in ventricular filling pressures.
Option C: The vasodilator effect of amrinone decreases peripheral vascular resistance. Indeed, an increase in cyclic adenosine phosphate within the vascular smooth muscle causes a reduction in the intracellular calcium concentration; subsequently, relaxing the vascular smooth muscle. This systemic vasodilation results in a decrease in total peripheral and pulmonary vascular resistance, reducing both preload and afterload.
Option D: Any increase in cardiac output will enhance renal perfusion; this is not just specific to amrinone. The subsequent relative ease in which blood can flow around the vascular network in combination with a stronger heartbeat increases stroke volume and, potentially, cardiac output. It is these vasodilatory and positive inotropic effects that are central in reversing the potentially deadly symptoms of heart failure.